Air can enter a hydronic (hot water) heating system in number of ways. Most typically, air enters the system as a result of some repair or replacement of a component of the system. If, for example, a boiler is replaced, the entire system typically must be drained and refilled with water.
The removal of air in a hot water heating system is conventionally done in two steps. The first step is to remove the large pockets of air by purging the system with a hose. The second step is to remove the left-over smaller pockets of air by an air scoop or microbubbler.
In the first step, a shut-off valve is opened on the fill line leading to the boiler and the system is filled until 12 psi is reached. Then a hose is attached to a drain valve in the system piping and the shut-off valves for each split, off of each zone, are closed. The drain valve is opened and the pressure is increased in the system by adjusting the fill valve to let water into the system. If that doesn""t work, the fill valve must be bypassed with a double-end hose. Most of the time the drain valves are not properly placed to do this. The water is then circulated through the system until new water replaces the water already in the system. The hose is then moved to the next drain valve and the step of circulating water to replace existing water with new water is repeated for each split of each heating loop. This task takes 1.25-2.5 hours and must be added to every repair done in the system. If the fill valve breaks due to excessive pressures during filling of the system, the entire process may have to be repeated.
In the second step, after the biggest pockets of air are gone, small bubbles remain, causing gurgling noises in the pipes of the hot water system. These small bubbles are removed by air scoops or microbubblers installed in the system. If properly installed, these devices will eventually purge most of the remaining air within 24 hours and the system should circulate smoothly and quietly.
If the smaller bubbles are not removed, they can accumulate into bigger pockets of air. These large pockets of air, if they are drawn through the system to the impeller chamber of the circulator, can cause stalling of circulation of the water through the system, so that no heat is delivered to the radiators located downstream of the circulator. In other cases, the air pocket can become trapped in one of the zones of the heating system, preventing circulation through that zone. If these problems occur in the winter, there is the possibility of the pipes freezing and bursting if the problems are not promptly solved.
A number of systems have been proposed to provide gas separation equipment in a hyrdronic heating system, but to date, none of the proposed systems have been suitable for use in retrofit applications, i.e., installation into preexisting hydronic heating systems. Thus, the system in U.S. Pat. No. 3,290,864 is complicated, and would require expensive repiping to install in a preexisting system due to the non-standard positioning of the pump inlet and outlet; and due to the inability to install the pump where system piping is run close to a wall. The system in U.S. Pat. No. 4,775,292 is not suitable for orientation in more than one direction, thus limiting its application to limited situations where a preexisting circulator pump is oriented in the same way as the intended use of the system shown in this patent. In addition, this system would not be useful to install the pump where system piping runs close to a wall.
More recently, I have invented a new design for a retrofit circulator, as disclosed in U.S. Pat. No. 6,129,523, issued Oct. 10, 2000, which provides a circulator for hydronic systems which can automatically remove air in the system, without need for laborious hose purging of the system, and which is suitable for retrofit applications regardless of the positioning or orientation of the existing circulator or piping in the system.
The present invention improves upon and extends this original design.
In accordance with one embodiment of the invention, an air purging circulator comprises a pump housing which is tapered from an inlet end to a pump end. In the preferred embodiment, the housing is a horizontal frustoconical shape, similar to a coffee cup positioned on a horizontal axis. The circulator has an inlet aperture and an outlet aperture at one end, generally axially aligned with each other. The inlet leads to a reservoir and from there to an impeller chamber. The impeller chamber is at one end of the housing and contains an impeller driven by an electric motor at an end of the circulator opposite from the end containing the inlet and outlet. The impeller chamber preferably connects to the outlet aperture in the pump housing by a curved passageway that extends from the impeller chamber to the outlet aperture.
The air purging circulator is particularly well adapted to use in retrofit of existing systems, even where piping is close by a wall. Preferably, the distance between the inlet and outlet apertures of the pump housing is selected to match the distance between flanges in conventional circulators, to allow easy retrofit.
The air purging reservoir is sized to provide reduction of the velocity of the circulating water in the hydronic system as it passes through the air purging reservoir on the suction side of the reservoir. This location has the lowest pressure within the system, and thus, the least amount of dissolved air in the circulating water. The air contained in the circulating water separates from the circulating water and, due to the frustoconical shape of the reservoir, collects in an upper portion of the air purging reservoir. The air purging reservoir has an air vent provided in the upper portion thereof to release the air collected in the reservoir. Preferably, the air purging reservoir is provided with four apertures positioned at 90xc2x0 intervals around a peripheral wall thereof. In this way, the air purging circulator may be oriented in any direction and the air vent will be positioned on the upper portion of the air purging reservoir.
In a preferred embodiment, the reservoir contains a separation media, such as a plate, marbles, wire mesh, or crumpled wire, to further slow the water flow and enhance separation of the air from the water.
Other objects, aspects and features of the present invention in addition to those mentioned above will be pointed out in or will be understood from the following detailed description provided in conjunction with the accompanying drawings.